On the outer edge of human strength and effort, a fitness coach molds clients for competition—and life.

High above Las Vegas, in a suite at the Palms, Denise Dinger is acting as matriarch of a trippy family whose obsession isn’t spelling bees or stringed instruments or dance. It’s human muscle and the display of it.

Her charges—“my girls,” she calls them—are nervous and a little giggly, butterflies before they take the stage at the Palms for the Jay Cutler Desert Classic, an amateur bodybuilding event. Then again, it could be the monastic diet Dinger has had them on the past few weeks. The suite smells of poached chicken and asparagus—and spray tan, which is applied liberally. Dinger does hair and makeup, and the scene has the atmosphere of a makeshift dressing room hours before a school play’s opening night, when no one in the world understands what they’re feeling. Except, of course, for Dinger. She has 14 competitors, and she’s as tense as her girls, though she doesn’t need to be. If they were Marines, they would charge a hill for her. They are ripped and ready.

Dinger is 50 years old, 5 feet tall and 130 pounds, though her weight fluctuates depending where she is in her competitive training. Her body fat sits around 9 percent. She has the physique of a comic-book hero—striated muscles like thick cables, muscles in places you didn’t even realize humans could have muscles. Her body is the result of the intense workout regimen and strict diet she’s lived for decades.

To watch Dinger work out is to see the outer edge of human strength, endurance and effort. She sits on a bench for shoulder presses, easily lifting two 20-pound dumbbells, completing eight repetitions. Then she does the same with 25 pounds, then 35, then 40—no rest!—then 45, and finally 50. She lifts the 50s to her knees, then her shoulders and then raises them, beginning her reps. She looks like she’s in childbirth. “Yes!” she finally exclaims.

Dinger is training for a July competition in Pittsburgh, and already today she’s spent 45 minutes on the stairs, before starting weights. After, she’ll head to a high school to run up the bleachers and do sprints on the track with her husband and son. The 1,800 calories she’ll consume are long gone.

Her own self-flagellating routine gives her credibility with her clients. “It’s one thing to tell people, but to practice what you preach is a whole ’nother story,” says Amanda Friedeck, who is training with Dinger for her third competition.

And yet, despite the toughness and competitive streak, her clients are family. “She’s like your mom, your trainer, your coach, your therapist,” says Ramona Ramjit-Munoz, who began training with Dinger in January. “She’s your friend, and with the weights, your enemy. But she’s awesome.”

Dinger epitomizes what scientists believe are the defining characteristics of humans’ multilevel evolution: a survival-of-the-fittest instinct that pushes some to compete and become stronger, blended with a unique capacity for collaboration and altruism. Let’s just call it love.

denise dinger came here in 1973 from Johannesburg, South Africa, as a young girl to study dance, her first love. By her mid-teens, however, she’d developed an eating disorder and later used cocaine and methamphetamines as appetite suppressants. “It was just the ’70s,” she explains. “That’s what we did.”

She would struggle with substance abuse for the better part of two decades. “I lived a double life. You would never know.”

She was on the road dancing and would later perform aerial ballet at Circus Circus. She taught dance to preschoolers, served as an aerobics instructor and earned a black belt in Shotokan karate. In 1986, she took up bodybuilding and went on to become the Nevada lightweight champion in 1990.

Meanwhile, she began having children, now aged 25, 18, 16 and 13. (Dinger says she never used drugs during her pregnancies.) She married her husband Craig 20 years ago, and went into recovery 16 years ago. But the eating disorder and its underlying issue, body dysmorphia—an obsession with perceived flaws in physical appearance—will always stalk her, Dinger says. “It’s a big deal for me to eat a piece of cheesecake. It’s crazy, but it’s a crazy disease, and I will have it the rest of my life.”

I ask if she’s replaced her old compulsions—drugs and weight loss—with another one, fitness. “Pick my poison. Do I stay inside my disease? Or do I try to live a healthy, somewhat normal life, raising my kids.” The old way is no way at all, she says, and so she trains and trains and trains. “Dude, I’m 50; I’m still truckin’. I’m still competing.”

Jeanie Lyons of Las Vegas, a Dee's Diva and competitor in the figure category, warms up with weights backstage at the Jay Cutler Desert Classic at the Palms on Saturday, April 7, 2012.

Now, she and Craig have their own personal training business, Dee’s Divas and Dudes, and Dinger is something of an icon in the Vegas fitness community. Their specialty is preparing men and women—mostly women—for competitions like the Cutler Desert Classic, and Dinger’s particular expertise is the proper diet for competitions. She can look at a competitor and tell what they’ve been eating. After recommending that a client eat more protein, specifically steak, she admired the change in muscle tone. Other times, she’ll move them to chicken and fish for a leaner look.

And, in a sport plagued with body dysmorphia, her own history helps her guide athletes and steer them away from eating disorders. She’s as much a therapist and life coach as a bodybuilding instructor.

Friedeck, 21, started with Dinger in January and is in the midst of a trio of competitions, including an upcoming national qualifying event in Culver City, California. She hopes to turn pro eventually, following in the footsteps of seven previous Dinger clients.

“When you start dieting and training the way you’re supposed to, you need support,” Friedeck says. “People who do competitions have their own community. You can talk to family and friends, but unless you’ve actually done it, people aren’t going to understand.”

The competitors have to eat near-identical meals at near-identical times, sometimes bringing their own food to social occasions. Dinger instructs them to eat seven small meals per day, from an extremely restricted set of options, including chicken and asparagus, broccoli, brown rice, fish, oatmeal and fruit, plus vitamins, amino acids, glutamine and other supplements. As I watch Dinger scarf down some mid-afternoon oatmeal, she’s honest: “It’s just gross,” she says with a laugh.

The diet can be as difficult as the workouts, but competitors know Dinger is right there with them because of her own competition schedule. Misery, company, etc.

“Like, you know how you wake up and brush your teeth without thinking about it? I wake up and do 45 minutes of cardio,” Friedeck says. That’s just the start of the day. More cardio will follow, and of course, weights.

Denise Dinger works out at City Athletic Club in Las Vegas on Wednesday, April 25, 2012.

I watched Dinger work out twice and joined in once. She laughed at me. “He’s strong for a little guy,” she said. She did 150 pounds in a seated row, 80 in a lat pulldown, rear deltoids, triceps and biceps, legs. The next time was all shoulders.

I ask Dinger how she gets to the other side, how she sees past the pain of the final reps. “What I’m thinking about is contracting that muscle. If I feel that pain, I know I’ll get to the other side.”

The men at City Athletic Club on Sahara, where she trains herself and her clients, treat her respectfully. Wise choice. “I’m sick strong,” she says joyfully. Dinger takes human growth hormone under a doctor’s supervision. HGH is controversial in many sports, but less so in bodybuilding, and Dinger is evangelical about its benefits for people older than 35 who want to continue building muscle. The medical community is still skeptical of its anti-aging benefits.

Not all of Dinger’s clients are as competitive as Friedeck. Many compete in the growing sport simply to seek focus. Bodybuilding has changed over the past few years, say Dinger and Jea Jung, owner of City Athletic Club and a former competitor.

“Historically, bodybuilding was about extreme physique development,” Jung says. “The people who could push their bodies to the furthest edge of what’s possible. They wanted the freakiest look. That has a certain appeal, but only to a small audience. As a business it was weak. It has evolved to draw a bigger audience.”

The hulking look on women—an obvious result of anabolic steroids—is not in favor anymore. New categories that emphasize traditional femininity have drawn new competitors and new fans. The fitness category has attracted former gymnasts and other athletes. And the bikini category, in which most of Dinger’s clients compete, is booming. At the Jay Cutler Classic, the Palms stage was packed with women in the bikini category.

Ramjit-Munoz, a 33-year-old dealer at the Stratosphere, hadn’t worked out consistently for a few years. She decided this would be her year, and like many of Dinger’s clients, she heard about Dinger through word-of-mouth, then decided to train with her. Dinger persuaded Ramjit-Munoz to take the next step and compete.

“My body transformed in front of me,” she says. Now, Ramjit-Munoz has a new family at the gym, and Dinger always knows what she’s thinking. “She’ll say, ‘Uh-huh, there’s something wrong. Do you wanna talk about it or not?’ And now I’m all babbling about stuff.”

Ramjit-Munoz says what began as physical fitness and changes to her diet became something more fundamental. “Now I’m like, ‘I can do anything,’” she says.

Dinger’s motto is, “Tell the mind, and the body will follow,” but her teaching works in the other direction, too. Extreme physical fitness can transform the mind.

Dinger says that’s her true goal. “When they come out of it, I want them to feel empowered, to have direction.” The competition, she says, is beside the point. “It’s not about winning. If you’re here for that, you’re here for the wrong reasons. You’re going to determine your self-worth based on someone’s opinion of you? That’s ridiculous.

“It’s about becoming a better person,” she says. “It’s about goals and how to achieve them. It’s about getting that job you want. It’s about saying what you wanted to say to that person you’re afraid of. It’s powerful.”